teach find_root_device to deal with /dev/ subdirs

(by "Kirill K. Smirnov" <lich@math.spbu.ru>)

1 files changed, 49 insertions, 10 deletions

diff --git a/libbb/find_root_device.c b/libbb/find_root_device.c
index ea360eae5..7182102c7 100644
--- a/libbb/find_root_device.c
+++ b/libbb/find_root_device.c
@@ -9,26 +9,65 @@
 
 #include "libbb.h"
 
-char *find_block_device(const char *path)
+/* Find block device /dev/XXX which contains specified file
+ * We handle /dev/dir/dir/dir too, at a cost of ~80 more bytes code */
+
+/* Do not reallocate all this stuff on each recursion */
+enum { DEVNAME_MAX = 256 };
+struct arena {
+        struct stat st;
+        dev_t dev;
+        /* Was PATH_MAX, but we recurse _/dev_. We can assume
+         * people are not crazy enough to have mega-deep tree there */
+        char devpath[DEVNAME_MAX];
+};
+
+static char *find_block_device_in_dir(struct arena *ap)
 {
         DIR *dir;
         struct dirent *entry;
-        struct stat st;
-        dev_t dev;
-        char *retpath=NULL;
+        char *retpath = NULL;
+        int len, rem;
+
+        dir = opendir(ap->devpath);
+        if (!dir)
+                return NULL;
 
-        if (stat(path, &st) || !(dir = opendir("/dev")))
+        len = strlen(ap->devpath);
+        rem = DEVNAME_MAX-2 - len;
+        if (rem <= 0)
                 return NULL;
-        dev = (st.st_mode & S_IFMT) == S_IFBLK ? st.st_rdev : st.st_dev;
+        ap->devpath[len++] = '/';
+
         while ((entry = readdir(dir)) != NULL) {
-                char devpath[PATH_MAX];
-                sprintf(devpath,"/dev/%s", entry->d_name);
-                if (!stat(devpath, &st) && S_ISBLK(st.st_mode) && st.st_rdev == dev) {
-                        retpath = xstrdup(devpath);
+                safe_strncpy(ap->devpath + len, entry->d_name, rem);
+                if (stat(ap->devpath, &ap->st) != 0)
+                        continue;
+                if (S_ISBLK(ap->st.st_mode) && ap->st.st_rdev == ap->dev) {
+                        retpath = xstrdup(ap->devpath);
                         break;
                 }
+                if (S_ISDIR(ap->st.st_mode)) {
+                        /* Do not recurse for '.' and '..' */
+                        if (DOT_OR_DOTDOT(entry->d_name))
+                                continue;
+                        retpath = find_block_device_in_dir(ap);
+                        if (retpath)
+                                break;
+                }
         }
         closedir(dir);
 
         return retpath;
 }
+
+char *find_block_device(const char *path)
+{
+        struct arena a;
+
+        if (stat(path, &a.st) != 0)
+                return NULL;
+        a.dev = S_ISBLK(a.st.st_mode) ? a.st.st_rdev : a.st.st_dev;
+        strcpy(a.devpath, "/dev");
+        return find_block_device_in_dir(&a);
+}